| Domen Puncer | daa7382 | 2007-04-18 12:11:05 +0200 | [diff] [blame] | 1 | Lite5200B wakeup from low-power mode (CONFIG_LITE5200B_PM) |
| 2 | ---------------------------------------------------------- |
| 3 | |
| 4 | Low-power mode as described in Lite5200B User's Manual, means that |
| 5 | with support of MC68HLC908QT1 microcontroller (refered to as QT), |
| 6 | everything but the SDRAM can be powered down. This brings |
| 7 | maximum power saving, while one can still restore previous state |
| 8 | quickly. |
| 9 | |
| 10 | Quick overview where U-Boot comes into the picture: |
| 11 | - OS saves device states |
| 12 | - OS saves wakeup handler address to physical 0x0, puts SDRAM into |
| 13 | self-refresh and signals to QT, it should power down the board |
| 14 | - / board is sleeping here / |
| 15 | - someone presses SW4 (connected to QT) |
| 16 | - U-Boot checks PSC2_4 pin, if QT drives it down, then we woke up, |
| 17 | so get SDRAM out of self-refresh and transfer control to OS |
| 18 | wakeup handler |
| 19 | - OS restores device states |
| 20 | |
| 21 | This was tested on Linux with USB and Ethernet in use. Adding |
| 22 | support for other devices is an OS issue. |